Is it racist to mention race if a criminal suspect isn’t White?

No! It’s a way to identify someone or narrow the search for someone quickly. It’s a descriptive comment exactly the same as; gender, build, height, hair color/style, clothing, tattoos etc.

What is racist – in my opinion – is when the news media limits the use of this identifier!

Race is an identifier, nothing more nothing less!
For example, the media reports words to the effect of -black suspect shot by police, which immediately implies that the incident is a racial one. It of course ignores that police is a profession and not a race, and it ignores the race of the officer involved – unless it fits into the narrative that the police disproportionately use violence or the officer was White...

Let’s say a robbery takes place, the suspect has produced a gun and threatened someone leaving the scene stealing the person’s cellphone and cash. They’ve made off on foot into the crowd. Police need to quickly know, the description of the suspect in order to detain them and prevent further violence. The ethnicity of the suspect is a huge part of identifying them quickly! If someone says it’s a White male, aged 20 – 25 with a bushy beard, they can quickly rule out a lot of other people.

So, no it’s not racist to mention race or ethnicity! 

You are literally just describing the suspect. People seem to have really botched their understandings on what racism is these days. Let me try something to make it absolutely clear; it would not be racist for someone to say “a black man stole my bicycle”. Now, realistically they will likely give more detail than that, like an estimate of their height, and weight, with some key facial features. However, the race of the suspect in this instance is a very important detail! It immediately rules out a lot of men in the population. Presumably if you are saying this it is because you actually saw the man in question and this is an accurate representation of what you observed.

Now on the other hand, if someone said “somebody stole my bike, I bet they were black”, well that will be considered racist. The reason being, this implies they didn’t see who did it, it’s not descriptive, its prescriptive. They are making a value judgement of a person they didn’t see  based on a preconception.